Problem: Express your answer in scientific notation. $2.8\cdot10^{-3} -0.00065 = $
Solution: $\phantom{=}{ 2.8\cdot10^{-3}} -0.00065 $ $={2.8 \cdot 10^{-3}} - 6.5\cdot10^{-4} $ $={28 \cdot 10^{-4}} - 6.5\cdot10^{-4} $ $= (28-6.5)\cdot10^{-4}$ $=21.5\cdot10^{-4}$ $= 2.15\cdot10^{-3}$